The present invention relates generally to an optical sensor and more particularly to an optical sensor for detecting an object within an area of interest.
Optical sensors are used in a wide variety of applications, such as in robotics, touch screen devices and digital cameras. These optical sensors typically use either a complementary metal oxide semiconductor (“CMOS”) or a charge coupled device (“CCD”) type of sensor. The sensors use light sensitive circuitry, commonly referred to as a pixel, to convert light energy into electrical energy. Each pixel typically includes a photodiode formed in a silicon substrate. As the photodiode is exposed to light, an electrical charge is induced. The level of the charge indicates amount of light and a level of contrast can be determined by calibrating the electrical charge to a color scale. The color of the image may be determined by using either filters over the pixels or by having pixels with photodiodes that only react to certain wavelengths of light.
While optical sensors are used in a wide variety of applications, its use in some applications can be hampered due to cost. Low cost sensors are used in some applications, such as in computer mice for example, that are well defined and reasonably controlled. Otherwise environmental effects, such as ambient light for example, interfere with the operation of the sensor. In the case of the computer mouse, the sensor needs to be close to the surface with the mouse resting against the surface to block out light. If the mouse is lifted even a small amount, operation ceases. This limitation restricts the wide adoption of low cost optical sensors into applications where the sensor may be installed outdoors, or in an equipment room that is normally dark and periodically exposed to varying light conditions.
The use of optical sensors in remote applications has also been hampered by power requirements. Remote locations may be any location where an external electrical power supply may not be readily available. Without an external energy supply, the optical sensor must rely on some type of battery-type storage system. Since the replacement of batteries increases the maintenance costs associated with the optical sensor, operators typically find it desirable to minimize power consumption. This power requirement may also create an issue with control circuitry. Image analysis can be a computationally intensive operation that requires one or more fast processors and extended computation time. Generally, the faster the processor and the longer the computation time, the more energy is consumed.
Thus, while existing sensing devices are suitable for their intended purposes, there remains a need for improvements. In particular, there remains a need for improvements in providing reliable, accurate and cost effective methods and systems for operating an optical sensor that can be used in a wide variety of applications with minimal power consumption. There also remains a need for improvements in analyzing acquired images that minimizes computation requirements and energy consumption.